Local IL-23 is required for proliferation and retention of skin-resident memory TH17 cells

Spatial Transcriptomics in Inflammatory Skin Diseases Using GeoMx Digital Spatial Profiling: A Practical Guide for Applications in Dermatology

The spatial organization of the skin is critical for its function. In particular, the skin immune microenvironment is arranged spatially and temporally, such that imbalances in the immune milieu are indicative of disease. Spatial transcriptomic platforms are helping to provide additional insights into aberrant inflammation in tissues that are not captured by tissue processing required for single-cell RNA sequencing. In this paper, we discuss a technical and user experience overview of NanoString's GeoMx Digital Spatial Profiler to perform in-depth spatial analysis of the transcriptome in inflammatory skin diseases. Our objective is to provide potential pitfalls and methods to optimize RNA capture that are not readily available in the manufacturer's guidelines. We use concrete examples from our experiments to demonstrate these strategies in inflammatory skin diseases, including psoriasis, lichen planus, and discoid lupus erythematosus. Overall, we hope to illustrate the potential of digital spatial profiling to dissect skin disease pathogenesis in a spatially resolved manner and provide a framework for other skin biology investigators using digital spatial profiling.

The role and therapeutic strategies for tissue-resident memory T cells, central memory T cells, and effector memory T cells in psoriasis

Psoriasis is a skin disease that is inflammatory and persistent, causing a high rate of recurrence, poor quality of life, and significant socioeconomic burden. Its main pathological manifestations are abnormal activation and infiltration of T cells and excessive proliferation of keratinocytes (KCs). The great majority of patients with psoriasis will relapse after remission. It usually lasts a lifetime and necessitates long-term treatment strategies. During periods of activity and remission, one of the main cell types in psoriasis is memory T cells, which include tissue-resident memory T (TRM) cells, central memory T (TCM) cells, and effector memory T (TEM) cells. They work by releasing inflammatory factors, cytotoxic particles, or altering cell subpopulations, leading to increased inflammation or recurrence. This review summarizes the role of memory T cells in the pathology and treatment of psoriasis, with a view to potential novel therapies and therapeutic targets.

Skin-resident T Cells Contribute to the Dynamic Disease Manifestations of Psoriasis

The human skin forms a dynamic barrier to physical injuries and microbial invasion. Constant interactions between stroma and tissue-confined immune cells maintain skin homeostasis. However, the cellular interactions that maintain skin health also contribute to focal immunopathology. Psoriasis is a common disease that manifests with focal pathology induced by environmental triggers in genetically susceptible individuals. Within psoriasis plaques, cross-talk between skin-resident T cells and stroma cells leads to chronic inflammation. Inflammatory cytokines such as TNF-α, IL-17, IL-22, and IL-23 amplify the local chronic inflammation and sustain the well-demarcated thick and scaly plaques that characterize the disease. In resolved lesions, T cells remain poised for IL-17 and IL-22 production, and postinflammatory epigenetic modifications lower the threshold for initiation of local relapse. This review focuses on how tissue-resident memory T cells contribute to the onset, maintenance, resolution, and relapse of psoriasis.

Injury-induced myosin-specific tissue-resident memory T cells drive immune checkpoint inhibitor myocarditis

Cardiac myosin-specific (MyHC) T cells drive the disease pathogenesis of immune checkpoint inhibitor-associated myocarditis (ICI-myocarditis). To determine whether MyHC T cells are tissue-resident memory T (TRM) cells, we characterized cardiac TRM cells in naive mice and established that they have a distinct phenotypic and transcriptional profile that can be defined by their upregulation of CD69, PD-1, and CXCR6. We then investigated the effects of cardiac injury through a modified experimental autoimmune myocarditis mouse model and an ischemia-reperfusion injury mouse model and determined that cardiac inflammation induces the recruitment of autoreactive MyHC TRM cells, which coexpress PD-1 and CD69. To investigate whether the recruited MyHC TRM cells could increase susceptibility to ICI-myocarditis, we developed a two-hit ICI-myocarditis mouse model where cardiac injury was induced, mice were allowed to recover, and then were treated with anti-PD-1 antibodies. We determined that mice who recover from cardiac injury are more susceptible to ICI-myocarditis development. We found that murine and human TRM cells share a similar location in the heart and aggregate along the perimyocardium. We phenotyped cells obtained from pericardial fluid from patients diagnosed with dilated cardiomyopathy and ischemic cardiomyopathy and established that pericardial T cells are predominantly CD69+ TRM cells that up-regulate PD-1. Finally, we determined that human pericardial macrophages produce IL-15, which supports and maintains pericardial TRM cells.

IL-17 in skin infections and homeostasis

Interleukin (IL) 17 is a proinflammatory cytokine belonging to a structurally related group of cytokines known as the IL-17 family. It has been profoundly studied for its contribution to the pathology of autoimmune diseases. However, it also plays an important role in homeostasis and the defense against extracellular bacteria and fungi. IL-17 is important for epithelial barriers, including the skin, where some of its cellular targets reside. Most of the research work on IL-17 has focused on its effects in the skin within the context of autoimmune diseases or sterile inflammation, despite also having impact on other skin conditions. In recent years, studies on the role of IL-17 in the defense against skin pathogens and in the maintenance of skin homeostasis mediated by the microbiota have grown in importance. Here we review and discuss the cumulative evidence regarding the main contribution of IL-17 in the maintenance of skin integrity as well as its protective or pathogenic effects during some skin infections.

S1PR1 mediates Th17 cell migration from the thymus to the skin in health and disease

Th17 cells play crucial roles in host defense and the pathogenesis of autoimmune diseases in the skin. While their differentiation mechanisms have been extensively studied, the origin of skin Th17 cells remains unclear. In this study, we analyzed single-cell RNA-sequencing data and identify the presence of Th17 cells in the human thymus. Thymic Th17 cells were characterized by high expression levels of Sphingosine-1-Phosphate Receptor 1 (S1PR1), a receptor crucial for T cell egress from lymphoid tissues. In mice, Th17 cell-specific knockout of S1pr1 resulted in the accumulation of Th17 cells in the thymus and a corresponding decrease in their numbers in the skin. Th17 cells that accumulated in the thymus exhibited a lower IL-17A production capacity compared to those in the skin, indicating that the local environment in the skin is important for maintaining the Th17 cell phenotype. Additionally, using a murine psoriasis model, we demonstrated that Th17 cell-specific knockout of S1pr1 reduced their migration to the inflamed skin, thereby ameliorating disease progression. Collectively, our data suggest that S1PR1 mediates Th17 cell migration from the thymus to the skin, thereby modulating their functional engagement in both homeostatic and inflammatory conditions.

Differential Pharmacodynamic Effects on Psoriatic Biomarkers by Guselkumab Versus Secukinumab Correlate with Long-Term Efficacy: An ECLIPSE Substudy

IL-23 is a cytokine produced by myeloid cells that drives the T helper 17 pathway and plays an essential role in the pathophysiology of plaque psoriasis. IL-23 activation initiates a cascade of cytokines subsequently inducing the expression of many psoriasis-related proteins. This study aimed to better understand the underlying mechanisms driving the differences between IL-23 and IL-17A blockade in patients with psoriasis and their implications for durability of clinical responses. Serum and/or skin biopsies were isolated from patients treated with guselkumab or secukinumab for evaluation of potential biomarkers of pharmacodynamic response to treatment. Guselkumab treatment led to significantly greater reductions of IL-17F and IL-22 serum levels than treatment with secukinumab at weeks 24 and 48, demonstrating sustained regulation of the IL-23/T helper 17 pathway. Analyses of proteomic and transcriptomic profiles of patient sera and skin biopsies demonstrated differential regulation of proteins involved in chemokine, TNF, and relevant immune signaling pathways to a greater degree with guselkumab than with secukinumab treatment. These data provide insights into the differences between the mechanisms and impact of IL-23 and IL-17A blockade in psoriasis, with implications for efficacy observations and treatment paradigms. Trial Registration: The original study was registered at ClinicalTrials.gov (NCT03090100).

How Can Spatial Transcriptomic Profiling Advance Our Understanding of Skin Diseases?

Spatial transcriptomic (ST) profiling is the mapping of gene expression within cell populations with preservation of positional context and represents an exciting new approach to develop our understanding of local and regional influences upon skin biology in health and disease. With the ability to probe from a few hundred transcripts to the entire transcriptome, multiple ST approaches are now widely available. In this paper, we review the ST field and discuss its application to dermatology. Its potential to advance our understanding of skin biology in health and disease is highlighted through the illustrative examples of 3 research areas: cutaneous aging, tumorigenesis, and psoriasis.

Thymopentapeptide Affects T-Cell Subsets by Modulating the Flora of the Skin Surface to Alleviate Psoriasis

Background

Psoriasis is a common chronic inflammatory skin condition. The emergence of psoriasis has been linked to dysbiosis of the microbiota on the skin surface and an imbalance in the immunological microenvironment. In this study, we investigated the therapeutic impact of topical thymopentin (TP5) on imiquimod (IMQ)-induced psoriasis in mice, as well as the modulatory influence of TP5 on the skin immune milieu and the skin surface microbiota.

Methods

The IMQ-induced psoriasis-like lesion mouse model was used to identify the targets and molecular mechanisms of TP5. Immunofluorescence was employed to identify differences in T-cell subset expression before and after TP5 therapy. Changes in the expression of NF-κB signaling pathway components were assessed using Western blotting (WB). 16S rRNA sequencing and network pharmacology were used to detect changes in the skin flora before and after TP5 administration.

Results

In vivo, TP5 reduced IMQ-induced back inflammation in mice. H&E staining revealed decreased epidermal thickness and inflammatory cell infiltration with TP5. Masson staining revealed decreased epidermal and dermal collagen infiltration after TP5 administration. Immunohistochemistry showed that TP5 treatment dramatically reduced IL-17 expression. Results of the immunoinfiltration analyses showed psoriatic lesions with more T-cell subsets. According to the immunofluorescence results, TP5 dramatically declined the proportions of CD4+, Th17, ROR+, and CD8+ T cells. WB revealed that TP5 reduced NF-κB pathway expression in skin tissues from IMQ-induced psoriasis model mice. 16S rRNA sequencing revealed a significant increase in Burkholderia and Pseudomonadaceae_Pseudomonas and a significant decrease in Staphylococcaceae_Staphylococcus, Aquabacterium, Herbaspirillum, and Balneimonas. Firmicutes dominated the skin microbial diversity after TP5 treatment, while Bacteroidetes, Verrucomicrobia, TM7, Proteobacteria, Actinobacteria, Acidobacteria, Gemmatimonadetes, and other species dominated in the IMQ group.

Conclusion

TP5 may treat psoriasis by modulating the epidermal flora, reducing NF-κB pathway expression, and influencing T-cell subsets.

Inflammatory memory in psoriasis: From remission to recurrence

The routine use of targeted systemic immunomodulatory therapies has transformed outcomes for people with severe psoriasis, with skin clearance (clinical remission) rates up to 60% at 1 year of biologic treatment. However, psoriasis may recur following drug withdrawal, and as a result, patients tend to continue receiving costly treatment indefinitely. Here, we review research into the "inflammatory memory" in resolved psoriasis skin and the potential mechanisms leading to psoriasis recurrence following drug withdrawal. Research has implicated immune cells such as tissue resident memory T cells, Langerhans cells, and dermal dendritic cells, and there is growing interest in keratinocytes and fibroblasts. A better understanding of the interactions between these cell populations, enabled by single cell technologies, will help to elucidate the events underpinning the shift from remission to recurrence. This may inform the development of personalized strategies for sustaining remission while reducing long-term drug burden.

IL-17 Control of Cutaneous Immune Homeostasis

IL-17 is widely recognized for its roles in host defense and inflammatory disorders. However, it has become clear that IL-17 is also an essential regulator of barrier tissue physiology. Steady-state microbe sensing at the skin surface induces low-level IL-17 expression that enhances epithelial integrity and resists pathogens without causing overt inflammation. Recent reports describe novel protective roles for IL-17 in wound healing and counteracting physiologic stress; however, chronic amplification of these beneficial responses contributes to skin pathologies as diverse as fibrosis, cancer, and autoinflammation. In this paper, we discuss the context-specific roles of IL-17 in skin health and disease and therapeutic opportunities.

Heterogeneity and plasticity of tissue-resident memory T cells in skin diseases and homeostasis: a review

Skin tissue-resident memory T (Trm) cells are produced by antigenic stimulation and remain in the skin for a long time without entering the peripheral circulation. In the healthy state Trm cells can play a patrolling and surveillance role, but in the disease state Trm cells differentiate into various phenotypes associated with different diseases, exhibit different localizations, and consequently have local protective or pathogenic roles, such as disease recurrence in vitiligo and maintenance of immune homeostasis in melanoma. The most common surface marker of Trm cells is CD69/CD103. However, the plasticity of tissue-resident memory T cells after colonization remains somewhat uncertain. This ambiguity is largely due to the variation in the functionality and ultimate destination of Trm cells produced from memory cells differentiated from diverse precursors. Notably, the presence of Trm cells is not stationary across numerous non-lymphoid tissues, most notably in the skin. These cells may reenter the blood and distant tissue sites during the recall response, revealing the recycling and migration potential of the Trm cell progeny. This review focuses on the origin and function of skin Trm cells, and provides new insights into the role of skin Trm cells in the treatment of autoimmune skin diseases, infectious skin diseases, and tumors.

Joint-specific memory, resident memory T cells and the rolling window of opportunity in arthritis

In rheumatoid arthritis, juvenile idiopathic arthritis and other forms of inflammatory arthritis, the immune system targets certain joints but not others. The pattern of joints affected varies by disease and by individual, with flares most commonly involving joints that were previously inflamed. This phenomenon, termed joint-specific memory, is difficult to explain by systemic immunity alone. Mechanisms of joint-specific memory include the involvement of synovial resident memory T cells that remain in the joint during remission and initiate localized disease recurrence. In addition, arthritis-induced durable changes in synovial fibroblasts and macrophages can amplify inflammation in a site-specific manner. Together with ongoing systemic processes that promote extension of arthritis to new joints, these local factors set the stage for a stepwise progression in disease severity, a paradigm for arthritis chronicity that we term the joint accumulation model. Although durable drug-free remission through early treatment remains elusive for most forms of arthritis, the joint accumulation paradigm defines new therapeutic targets, emphasizes the importance of sustained treatment to prevent disease extension to new joints, and identifies a rolling window of opportunity for altering the natural history of arthritis that extends well beyond the initiation phase of disease.

Epithelial-derived interleukin-23 promotes oral mucosal immunopathology

At mucosal surfaces, epithelial cells provide a structural barrier and an immune defense system. However, dysregulated epithelial responses can contribute to disease states. Here, we demonstrated that epithelial cell-intrinsic production of interleukin-23 (IL-23) triggers an inflammatory loop in the prevalent oral disease periodontitis. Epithelial IL-23 expression localized to areas proximal to the disease-associated microbiome and was evident in experimental models and patients with common and genetic forms of disease. Mechanistically, flagellated microbial species of the periodontitis microbiome triggered epithelial IL-23 induction in a TLR5 receptor-dependent manner. Therefore, unlike other Th17-driven diseases, non-hematopoietic-cell-derived IL-23 served as an initiator of pathogenic inflammation in periodontitis. Beyond periodontitis, analysis of publicly available datasets revealed the expression of epithelial IL-23 in settings of infection, malignancy, and autoimmunity, suggesting a broader role for epithelial-intrinsic IL-23 in human disease. Collectively, this work highlights an important role for the barrier epithelium in the induction of IL-23-mediated inflammation.

The Immunology of Psoriasis-Current Concepts in Pathogenesis

Psoriasis is one of the most common inflammatory skin diseases with a chronic, relapsing-remitting course. The last decades of intense research uncovered a pathological network of interactions between immune cells and other types of cells in the pathogenesis of psoriasis. Emerging evidence indicates that dendritic cells, TH17 cells, and keratinocytes constitute a pathogenic triad in psoriasis. Dendritic cells produce TNF-α and IL-23 to promote T cell differentiation toward TH17 cells that produce key psoriatic cytokines IL-17, IFN-γ, and IL-22. Their activity results in skin inflammation and activation and hyperproliferation of keratinocytes. In addition, other cells and signaling pathways are implicated in the pathogenesis of psoriasis, including TH9 cells, TH22 cells, CD8+ cytotoxic cells, neutrophils, γδ T cells, and cytokines and chemokines secreted by them. New insights from high-throughput analysis of lesional skin identified novel signaling pathways and cell populations involved in the pathogenesis. These studies not only expanded our knowledge about the mechanisms of immune response and the pathogenesis of psoriasis but also resulted in a revolution in the clinical management of patients with psoriasis. Thus, understanding the mechanisms of immune response in psoriatic inflammation is crucial for further studies, the development of novel therapeutic strategies, and the clinical management of psoriasis patients. The aim of the review was to comprehensively present the dysregulation of immune response in psoriasis with an emphasis on recent findings. Here, we described the role of immune cells, including T cells, B cells, dendritic cells, neutrophils, monocytes, mast cells, and innate lymphoid cells (ILCs), as well as non-immune cells, including keratinocytes, fibroblasts, endothelial cells, and platelets in the initiation, development, and progression of psoriasis.

Environmental pollutants and phosphoinositide signaling in autoimmunity

Environmental pollution stands as one of the most critical challenges affecting human health, with an estimated mortality rate linked to pollution-induced non-communicable diseases projected to range from 20% to 25%. These pollutants not only disrupt immune responses but can also trigger immunotoxicity. Phosphoinositide signaling, a pivotal regulator of immune responses, plays a central role in the development of autoimmune diseases and exhibits high sensitivity to environmental stressors. Among these stressors, environmental pollutants have become increasingly prevalent in our society, contributing to the initiation and exacerbation of autoimmune conditions. In this review, we summarize the intricate interplay between phosphoinositide signaling and autoimmune diseases within the context of environmental pollutants and contaminants. We provide an up-to-date overview of stress-induced phosphoinositide signaling, discuss 14 selected examples categorized into three groups of environmental pollutants and their connections to immune diseases, and shed light on the associated phosphoinositide signaling pathways. Through these discussions, this review advances our understanding of how phosphoinositide signaling influences the coordinated immune response to environmental stressors at a biological level. Furthermore, it offers valuable insights into potential research directions and therapeutic targets aimed at mitigating the impact of environmental pollutants on the pathogenesis of autoimmune diseases. SYNOPSIS: Phosphoinositide signaling at the intersection of environmental pollutants and autoimmunity provides novel insights for managing autoimmune diseases aggravated by pollutants.

Resident memory T cells in nonlesional skin and healed lesions of patients with chronic inflammatory diseases: Appearances can be deceptive

Tissue-resident memory T (TRM) cells serve as a first line of defense in peripheral tissues to protect the organism against foreign pathogens. However, autoreactive TRM cells are increasingly implicated in autoimmunity, as evidenced in chronic autoimmune and inflammatory skin conditions. This highlights the need to characterize their phenotype and understand their role for the purpose of targeting them specifically without affecting local immunity. To date, the investigation of TRM cells in human skin diseases has focused mainly on lesional tissues of patients. Accumulating evidence suggests that self-reactive TRM cells are still present in clinically healed lesions of patients and play a role in disease flares, but TRM cells also populate skin that is apparently normal. This review discusses the ontogeny of TRM cells in the skin as well as recent insights regarding the presence of self-reactive TRM cells in both clinically healed skin and nonlesional skin of patients with autoimmune and inflammatory skin conditions, with a particular focus on psoriasis, atopic dermatitis, and vitiligo.

Immunotherapy in cutaneous melanoma and biologics in psoriatic disease: similarities and differences from a clinical multidisciplinary perspective

INTRODUCTION

Immunomodulating therapies harness the power of the immune system to combat disease. In advanced melanoma, immune checkpoint inhibitors have significantly improved survival outcomes by activating the immune system to recognize and eliminate cancer cells. In psoriasis, interleukin inhibitors effectively suppress inflammation and improve disease symptoms.

AREAS COVERED

We provide a meta-opinion-based consensus paper on the analogies and differences in treatment mechanisms, duration, frequency between immunotherapy for advanced melanoma and biologics for psoriasis. Combining the current scientific evidence with expert insights, we provide valuable guidance for future research and decision-making processes.

EXPERT OPINION

The development of immunological treatments in melanoma and psoriasis has revolutionized dermatology, but the quest for tailored therapies that maximize efficacy continues. Managing cutaneous exacerbations during melanoma immunotherapy in psoriatic patients remains challenging. Similarly, treating oncologic psoriasis patients resistant to traditional therapies requires individualized approaches. Research is needed to identify response predictors in both conditions and address the sustainability of healthcare systems due to the high cost of biologics. Drug delay studies for psoriasis and longer follow-up evaluations after immunotherapy discontinuation in melanoma are essential for optimizing treatment outcomes and resource allocation.

Pediatric psoriasis: Understanding pathological conditions and advances in treatment

Psoriasis is a long-lasting skin disease that primarily affects the skin, nails, and joints and is characterized by inflammation. Genetic factors contribute to its development and environmental triggers can worsen symptoms. Pathologically, psoriasis is characterized by uncontrolled keratinocyte proliferation and abnormal differentiation, and histological features include acanthosis with inflammatory cell infiltration and neovascularization. Psoriasis often starts in childhood, with about one-third of cases beginning during this time. Its prevalence steadily increases from the ages of 1 to 18 years in a linear fashion. Young people with psoriasis often require treatment throughout their childhood and adolescence, and into adulthood. However, prolonged treatment may increase the risk of complications and adverse events, so it is important to adopt an effective treatment approach that minimizes this risk. In addition, psoriasis is often associated with various comorbidities that may place a great burden on the physical and mental health of the children beyond those due to psoriasis itself. To ensure good long-term health outcomes, individuals with psoriasis should undergo regular screening. Treatment should be provided not only for skin lesions, but also for any comorbidities; however, currently there is not enough evidence on the treatment of pediatric psoriasis and no globally agreed-on guidelines exist for treating psoriasis in children. This article describes the etiology, clinical symptoms, and disease burden of pediatric psoriasis, the pathological conditions and diagnosis of plaque psoriasis, psoriatic arthritis, and generalized pustular psoriasis, and the available treatments for these conditions in Japan.

A single-cell atlas of IL-23 inhibition in cutaneous psoriasis distinguishes clinical response

Psoriasis vulgaris and other chronic inflammatory diseases improve markedly with therapeutic blockade of interleukin-23 (IL-23) signaling, but the genetic mechanisms underlying clinical responses remain poorly understood. Using single-cell transcriptomics, we profiled immune cells isolated from lesional psoriatic skin before and during IL-23 blockade. In clinically responsive patients, a psoriatic transcriptional signature in skin-resident memory T cells was strongly attenuated. In contrast, poorly responsive patients were distinguished by persistent activation of IL-17-producing T (T17) cells, a mechanism distinct from alternative cytokine signaling or resistance isolated to epidermal keratinocytes. Even in IL-23 blockade-responsive patients, we detected a recurring set of recalcitrant, disease-specific transcriptional abnormalities. This irreversible immunological state may necessitate ongoing IL-23 inhibition. Spatial transcriptomic analyses also suggested that successful IL-23 blockade requires dampening of >90% of IL-17-induced response in lymphocyte-adjacent keratinocytes, an unexpectedly high threshold. Collectively, our data establish a patient-level paradigm for dissecting responses to immunomodulatory treatments.

Interleukin 23 receptor: Expression and regulation in immune cells

The importance of IL-23 and its specific receptor, IL-23R, in the pathogenesis of several chronic inflammatory diseases has been established, but the underlying pathological mechanisms are not fully understood. This review focuses on IL-23R expression and regulation in immune cells.

Short-term risk and long-term incidence rate of infection and malignancy with IL-17 and IL-23 inhibitors in adult patients with psoriasis and psoriatic arthritis: a systematic review and meta-analysis

The risk of infection and malignancy may be a concern for patients with psoriasis receiving interleukin (IL)-17 and IL-23 inhibitors, particularly with long-term treatments. We aimed to estimate the short-term risks and long-term incidence rates of infection and malignancy with IL-17 or IL-23 antagonists in adult patients with psoriasis and psoriatic arthritis through this comprehensive meta-analysis (PROSPERO registration number: CRD42022363127). We searched PubMed, MEDLINE, Web of Science and ClinicalTrials.gov until May 17, 2023 for randomized placebo-controlled trials and long-term (≥ 52 weeks) open-label extension studies. The estimates of short-term risk ratios (RRs) and long-term exposure-adjusted incidence rates (EAIRs) were pooled using R software 4.1.1 and STATA 16.0. This review included 45 randomized placebo-controlled studies and 27 open-label extension studies. Short-term RRs of serious infection, overall infection and malignancy were 1.45 (95% confidence intervals, 95% CI: 0.81-2.59), 1.20 (95% CI: 1.06-1.35), 0.83 (95% CI: 0.41-1.71) with IL-17 inhibitors; and 0.68 (95% CI: 0.38-1.22), 1.13 (95% CI: 1.00-1.28), 0.87 (95% CI: 0.37-2.04) with IL-23 inhibitors. Increased short-term risks of nasopharyngitis and Candida infection with IL-17 inhibitors were found. Long-term EAIRs of serious infection, overall infection, nonmelanoma skin cancer (NMSC), malignancies excluding NMSC, nasopharyngitis and upper respiratory tract infection were 1.11/100 patient-years (PYs), 57.78/100PYs, 0.47/100PYs, 0.24/100PYs, 15.07/100PYs, 8.52/100PYs, 3.41/100PYs with IL-17 inhibitors; and 1.09/100PYs, 48.50/100PYs, 0.40/100PYs, 0.43/100PYs, 10.75/100PYs, 5.84/100PYs with IL-23 inhibitors. Long-term EAIR of Candida infection was 3.41/100PYs with IL-17 inhibitors. No active or reactivated tuberculosis was ever reported in all the trials, and only a few cases of latent tuberculosis, hepatitis, and herpes zoster were reported during the long-term extension periods. No evidence of increased EAIRs of infection and malignancy with longer durations was found. Our study suggested that short-term risk and long-term incidence of infections and malignancies in psoriasis patients receiving IL-17 inhibitors and IL-23 inhibitors are generally low. However, close monitoring is required for nasopharyngitis and Candida infection with IL-17 inhibitors.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022363127.

CTRP4/interleukin-6 receptor signaling ameliorates autoimmune encephalomyelitis by suppressing Th17 cell differentiation

C1q/TNF-related protein 4 (CTRP4) is generally thought to be released extracellularly and plays a critical role in energy metabolism and protecting against sepsis. However, its physiological functions in autoimmune diseases have not been thoroughly explored. In this study, we demonstrate that Th17 cell-associated experimental autoimmune encephalomyelitis was greatly exacerbated in Ctrp4-/- mice compared with WT mice due to increased Th17 cell infiltration. The absence of Ctrp4 promoted the differentiation of naive CD4+ T cells into Th17 cells in vitro. Mechanistically, CTRP4 interfered with the interaction between IL-6 and the IL-6 receptor (IL-6R) by directly competing to bind with IL-6R, leading to suppression of IL-6-induced activation of the STAT3 pathway. Furthermore, the administration of recombinant CTRP4 protein ameliorated disease symptoms. In conclusion, our results indicate that CTRP4, as an endogenous regulator of the IL-6 receptor-signaling pathway, may be a potential therapeutic intervention for Th17-driven autoimmune diseases.

Signaling pathways and targeted therapies for psoriasis

Psoriasis is a common, chronic, and inflammatory skin disease with a high burden on individuals, health systems, and society worldwide. With the immunological pathologies and pathogenesis of psoriasis becoming gradually revealed, the therapeutic approaches for this disease have gained revolutionary progress. Nevertheless, the mechanisms of less common forms of psoriasis remain elusive. Furthermore, severe adverse effects and the recurrence of disease upon treatment cessation should be noted and addressed during the treatment, which, however, has been rarely explored with the integration of preliminary findings. Therefore, it is crucial to have a comprehensive understanding of the mechanisms behind psoriasis pathogenesis, which might offer new insights for research and lead to more substantive progress in therapeutic approaches and expand clinical options for psoriasis treatment. In this review, we looked to briefly introduce the epidemiology, clinical subtypes, pathophysiology, and comorbidities of psoriasis and systematically discuss the signaling pathways involving extracellular cytokines and intracellular transmission, as well as the cross-talk between them. In the discussion, we also paid more attention to the potential metabolic and epigenetic mechanisms of psoriasis and the molecular mechanistic cascades related to its comorbidities. This review also outlined current treatment for psoriasis, especially targeted therapies and novel therapeutic strategies, as well as the potential mechanism of disease recurrence.

T cell and bacterial microbiota interaction at intestinal and skin epithelial interfaces

Graphical Abstract.

Resident cutaneous memory T cells: a clinical review of their role in chronic inflammatory dermatoses and potential as therapeutic targets

Resident memory T cells (T-RMs) remain in epithelial barrier tissues after antigen exposure and the initial effector phase. These T-RMs provide effective antimicrobial and anticancer immunity; however, pathogenic T-RMs have been shown to mediate various chronic inflammatory disorders in a variety of tissue types. In the skin, T-RMs are referred to as resident cutaneous memory T cells (cT-RMs). Understanding the mechanisms leading to the development and establishment of these cT-RMs populations may allow for targeted treatments that provide durable responses in chronic immune-mediated skin diseases, even after cessation. In this review, we summarize the evidence on cT-RMs as drivers of chronic inflammatory dermatoses, including psoriasis, vitiligo, atopic dermatitis, cutaneous lupus erythematosus and alopecia areata, among others. Data from in vitro, animal model and ex vivo human studies are presented, with a focus on the potential for cT-RMs to trigger acute disease flares, as well as recurrent disease, by establishing an immune 'memory' in the skin. Furthermore, the available data on the potential for existing and novel treatments to affect the development or survival of cT-RMs in the skin are synthesized. The data suggest a dynamic and rapidly growing area in the field of dermatology; however, we also discuss areas in need of greater research to allow for optimal treatment selection for long-term disease control.

Crosstalk: keratinocytes and immune cells in psoriasis

In the past, psoriasis was considered a skin disease caused only by keratinocyte disorders. However, the efficacy of immunosuppressive drugs and biologics used to treat psoriasis proves that psoriasis is an immune-mediated disease. Indeed, a variety of immune cells are involved in the pathogenesis of psoriasis, including dendritic cells, Th17 cells, and resident memory T cells. Furthermore, keratinocytes play a role in the development of psoriasis as immune cells by secreting antibacterial peptides, chemokines, tumor necrosis factor-α, interleukin (IL)-36, and IL-23. These immune cells and skin cells interact and drive the aberrant differentiation and proliferation of keratinocytes. This crosstalk between keratinocytes and immune cells critical in the pathogenesis of psoriasis forms an inflammatory loop, resulting in the persistence or exacerbation of psoriasis plaques.

Early disease intervention with guselkumab in psoriasis leads to a higher rate of stable complete skin clearance ('clinical super response'): Week 28 results from the ongoing phase IIIb randomized, double-blind, parallel-group, GUIDE study

BACKGROUND

Guselkumab is an interleukin (IL)-23 inhibitor with demonstrated efficacy in patients with psoriasis.

OBJECTIVES

Evaluate the impact of early disease intervention on clinical responses following 28 weeks of guselkumab treatment in patients with moderate-to-severe plaque psoriasis. Correlate clinical response and disease duration data with serum biomarker data.

METHODS

GUIDE is a phase IIIb randomized, double-blind, parallel-group, multicentre study of adults with moderate-to-severe plaque psoriasis. In study part 1, patients with a short disease duration (SDD [≤2 years]) or a long disease duration (LDD [>2 years]) received guselkumab 100 mg at Week (W) 0, 4, 12, and 20. Those achieving complete skin clearance at W20 and W28 were defined as a super responder (SRe). A multivariable logistic regression analysed the association between baseline factors and the likelihood of becoming an SRe. The relationship between clinical response, disease duration and serum biomarker data was assessed at W0 and 4.

RESULTS

In total, 880 patients were enrolled (SDD/LDD = 40.6%/59.4% of patients). More SDD than LDD patients achieved absolute Psoriasis Area and Severity Index (PASI) = 0 at W28 (51.8% vs. 39.4%) and were SRes (43.7% vs. 28.1% [overall 34.4%]). SDD patients also achieved PASI = 0 quicker than LDD patients (median 141 vs. 200 days). Disease duration and prior biologic use had the greatest impact on becoming an SRe, with no strong association among these independent variables. At baseline, there were no significant differences in the serum biomarker levels of IL-17A, IL-17F, IL-22 and β-defensin 2 between SDD and LDD patients, or between SRe and non-SRe patients. Guselkumab rapidly decreased these markers of systemic inflammation across all patient groups analysed at W4. Guselkumab was well tolerated.

CONCLUSIONS

Guselkumab efficacy was consistent across subpopulations, on the skin and systemically. The proportion of SRes was higher in SDD than LDD patients, indicating early treatment intervention may improve clinical outcomes.

Characteristics and sources of tissue-resident memory T cells in psoriasis relapse

Tissue-resident memory T cells (Trm) are a sub-population of memory T cells that reside in skin tissue. Recent studies have revealed potential role of Trm in the reoccurrence of psoriasis, as these cells tend to be profusely infiltrated in the lesions observed during psoriasis relapse. Trm can be classified into CD8+ Trm cells that are distributed mainly in the epidermis and CD4+ Trm cells in the dermis. CD8+ Trm is derived from circulating memory T cells and CD49a-CD8+ Trm takes a crucial role in psoriasis relapse. In contrast, CD4+ Trm may originate from exTh17 cells and exTreg cells emerging from the inflammatory process. Since IL-23 can activate Trm, neutralizing antibodies against IL-23 are suggested to be more effective in clinical treatment. This review will focus on Trm cells in psoriasis relapsed lesions to reveal their mechanisms in the pathogenesis, relapse and transformation of psoriasis.

Disease modification in inflammatory skin disorders: opportunities and challenges

Progress in understanding of the mechanisms underlying chronic inflammatory skin disorders, such as atopic dermatitis and psoriasis vulgaris, has led to new treatment options with the primary goal of alleviating symptoms. In addition, this knowledge has the potential to inform on new strategies aimed at inducing deep and therapy-free remission, that is, disease modification, potentially impacting on associated comorbidities. However, to reach this goal, key areas require further exploration, including the definitions of disease modification and disease activity index, further understanding of disease mechanisms and systemic spillover effects, potential windows of opportunity, biomarkers for patient stratification and successful intervention, as well as appropriate study design. This Perspective article assesses the opportunities and challenges in the discovery and development of disease-modifying therapies for chronic inflammatory skin disorders.

Candidiasis: From cutaneous to systemic, new perspectives of potential targets and therapeutic strategies

Candidiasis is an infection caused by fungi from a Candida species, most commonly Candida albicans. C. albicans is an opportunistic fungal pathogen typically residing on human skin and mucous membranes of the mouth, intestines or vagina. It can cause a wide variety of mucocutaneous barrier and systemic infections; and becomes a severe health problem in HIV/AIDS patients and in individuals who are immunocompromised following chemotherapy, treatment with immunosuppressive agents or after antibiotic-induced dysbiosis. However, the immune mechanism of host resistance to C. albicans infection is not fully understood, there are a limited number of therapeutic antifungal drugs for candidiasis, and these have disadvantages that limit their clinical application. Therefore, it is urgent to uncover the immune mechanisms of the host protecting against candidiasis and to develop new antifungal strategies. This review synthesizes current knowledge of host immune defense mechanisms from cutaneous candidiasis to invasive C. albicans infection and documents promising insights for treating candidiasis through inhibitors of potential antifungal target proteins.

Functional heterogeneity of human skin-resident memory T cells in health and disease

The human skin is populated by a diverse pool of memory T cells, which can act rapidly in response to pathogens and cancer antigens. Tissue-resident memory T cells (TRM ) have been implicated in range of allergic, autoimmune and inflammatory skin diseases. Clonal expansion of cells with TRM properties is also known to contribute to cutaneous T-cell lymphoma. Here, we review the heterogeneous phenotypes, transcriptional programs, and effector functions of skin TRM . We summarize recent studies on TRM formation, longevity, plasticity, and retrograde migration and contextualize the findings to skin TRM and their role in maintaining skin homeostasis and altered functions in skin disease.

Insulin Stimulates IL-23 Expression in Human Adipocytes: A Possible Explanation for the Higher Prevalence of Psoriasis in Obesity

Purpose

Psoriasis is a chronic systemic inflammatory disease involving the production of many pro-inflammatory cytokines derived from immune cells and interacting with different tissues leading to the typical skin lesions. Psoriasis shows a higher prevalence and a worse progression in obese than in lean subjects. The IL-23/IL-17 immune axis has a pivotal role in the pathogenesis of psoriasis and anti-IL-23 monoclonal antibodies are highly effective in its treatment. Since obesity in frequently associated with elevated insulin plasma levels, we have investigated the ability of in vitro differentiated human adipocytes to produce IL-23 at basal conditions and after insulin stimulation.

Material and Methods

In vitro differentiated human adipocytes were incubated in the absence and presence of different insulin concentrations and the expression of IL-23 was analyzed by real-time PCR and Western blotting.

Results

The results of this study show that in vitro differentiated human adipocytes spontaneously express IL-23 mRNA and protein being stimulated by insulin in a dose-dependent manner. The stimulatory effects of insulin on IL-23 expression were specific since it did not stimulate the expression of other well-known cytokines involved in psoriasis pathogenesis such as Il-22 nor LL-37. Furthermore, lipopolysaccharide did not stimulate IL-23 expression in human adipocytes, thus highlightening the specific effects of insulin in the stimulation of IL-23 expression in human adipocytes.

Conclusion

Here we show that human adipocytes spontaneously express IL-23 and that insulin stimulates IL-23 production by these cells in a specific manner as other stimuli, known to be involved in psoriasis pathophysiology, are ineffective. These observations could explain the association between psoriasis and obesity, a condition frequently characterized by a state of insulin hypersecretion.

Genetic underpinnings of the psoriatic spectrum

The psoriatic field includes both rare and common subtypes. Common complex forms include psoriasis vulgaris and psoriatic arthritis. In these subtypes, certain HLA alleles remain the most relevant genetic factors, although genome-wide association studies lead to the detection of more than 80 susceptibility loci. They mainly affect innate and adaptive immunity and explain over 28 % of the heritability. Pustular psoriasis comprises a group of rarer subtypes. Using exome sequencing, several disease genes were identified for mainly generalized pustular psoriasis, and an oligogenic inheritance is likely. Treatment studies based on the affected IL-36 pathway indicate a high response rate in this subtype further supporting the pathophysiological relevance of the affected gene products.

Novel potential therapeutic targets of alopecia areata

Alopecia areata (AA) is a non-scarring hair loss disorder caused by autoimmunity. The immune collapse of the hair follicle, where interferon-gamma (IFN-γ) and CD8+ T cells accumulate, is a key factor in AA. However, the exact functional mechanism remains unclear. Therefore, AA treatment has poor efficacy maintenance and high relapse rate after drug withdrawal. Recent studies show that immune-related cells and molecules affect AA. These cells communicate through autocrine and paracrine signals. Various cytokines, chemokines and growth factors mediate this crosstalk. In addition, adipose-derived stem cells (ADSCs), gut microbiota, hair follicle melanocytes, non-coding RNAs and specific regulatory factors have crucial roles in intercellular communication without a clear cause, suggesting potential new targets for AA therapy. This review discusses the latest research on the possible pathogenesis and therapeutic targets of AA.